errno 133 (EOWNERDEAD): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: A UCRT POSIX compatibility errno indicating that a robust mutex was acquired after its previous owner died.

Could be also:
Constant	Type	OS
ERROR_IS_JOIN_TARGET	Win32 error	Windows
EISCONN	errno	Solaris
SETUP_FAILURE	BugCheck Code	Windows

Previous	Next
EISCONN	ENOTCONN

EOWNERDEAD

EOWNERDEAD is a UCRT POSIX compatibility constant from the POSIX robust-mutex model. It means that the previous owner terminated while holding a robust mutex, and the caller has acquired that mutex with responsibility for deciding whether the protected state can be made consistent.

This is not an ordinary lock-acquisition failure. The caller may hold the lock even though the result reports EOWNERDEAD. Before allowing other users to observe the shared state, the new owner must validate or repair it and then follow the robust-mutex consistency procedure. Unlocking without repair can make the mutex permanently unusable, leading to ENOTRECOVERABLE.

Safe response sequence

Assume an update may have stopped between related writes.
Validate invariants, journal records, ownership metadata, and partially completed transactions.
Repair or rebuild the state only under the subsystem's documented recovery rules.
Mark the state consistent only after recovery succeeds; otherwise isolate it.

On Windows, the UCRT name alone does not make a native mutex robust. Identify the POSIX layer, third-party runtime, or abstraction that returned the status.

References

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